Ox66 fuel pump diaphragm symptoms?

[utfisherman]

Several people over the last 12 months have suggested replacing the fuel pumps to cure a variety of symptoms from excessive smoking, to loss of rpm, surging, and I think someone even mentioned removing warts. You mechanics out there: What symptoms are caused by small tears in the fuel pump diaphragms on Ox66 motors?

[John from Madison CT]

It's good to replace them every 3-4 years as preventative maintenance. Small tears in the diaphram will cause many weird symptoms.

[Hamfisted]

If you can't pump your fuel primer ball up firm with the motor OFF that's usually an indication of failed mechanical fuel pump diaphragm.
Excessive warts on the powerhead would be another ..... :))

-Mike

[BuzzB8]

[utfisherman]

Ok, I checked the powerhead, but did not find any warts. I do experience heavy smoke at startup. Yes, I know smoke is a good thing, but I can kill all the mosquitoes within 100 feet. I've read all the suggestions about tilting the motor after shutdown, but that does not work. I replaced the fuel primer bulb last year, and it works fine. I did notice that it will not hold pressure overnight like my old boat (slow diaphragm leak?). I can also alter the idle speed by tilting the motor down. If the motor is tilted beyond level (tucked under for takeoff) the idle speed will drop by 50 - 100 rpm). High speed operation seems ok. The oil pump was replaced under warranty two years ago, the O2 sensor last year (yeah, the old one really did go bad, it would not respond after cleaning) and the TPS and oil linkage adjustment are correct. Plugs are fine and I'm running the NGK "9" series. I suggested new fuel pump diaphragms last fall when the O2 sensor was replaced, but the mechanic did not feel it was an issue. Once again I am second guessing him. Hard for him to diagnosis properly when the water test lasts 10 minutes. Warranty runs out in Feb '08. I can live with it this summer again until the dealer slows down enough to get me in and out. But if these things are cheap and easy to replace, I'll do it myself. What do you think?

[skeeter202]

you can buy the complete pumps for $31 each on boats .net . I looked up the parts and time you buy gaskets , diaghrams etc you will have pretty close to that in it . go on there website , key in your info and you will see ..................

[Hamfisted]

Larry what brand oil are you using? Is the heavy smoke a definite oil smell? Like possible oil puddling in the crankcase during periods of non-use? Do you see any air pockets in any of the oil feed lines after the motor has sit (motor not run...) for a length of time? There are check valves in each oil feed tube to stop siphon type loss. If you see an air pocket or bubble in a line check it's check valve. Pop the hood and take a look with a flashlight prior to the next startup. There's also a O-ring seal on the oil pump drive shaft right behind the oil pump that may leak oil straight into the crankcase when it goes bad. How many hours on the motor now? When did the excessive smoke start occuring?


-Mike

[utfisherman]

Have always used Yamalube and ring-free per mechanic recommendation. The oil pump o-ring was replaced 12 months ago along with the oil pump. The motor is an '03 on an '04 hull. I have had it 2 years and put approx 80 hours on it. It was a bank repo so I have no prior history. I will check for air bubbles tomorrow before I fish our Thursday nighter. It is a blue haze as if extra oil is available at startup. The smoke cloud occurs the same way if we've been sitting 15 minutes or 1 hour. Smoke clears after 20 seconds, but last much longer and is very noticable when the engine is cold. At least nobody crowds me at the dock.

[utfisherman]

No air bubbles visible in oil supply hose between pump and fuel canister. This has been a problem since I bought the boat 2 years ago. My mechanic has been unable to properly diagnose the issue. The new oil pump and gaskets helped, but there is definitely a second problem. This possibly caused the failed o2 sensor. Yamaha warranty records showed the o2 sensor had also been replaced for the previous owner, so mine was not covered (they will replace once under warranty). I really appreciate the suggestions and feedback, but I've got to go fog for skeeters and smoke some Skeeters (sorry guys!) if the thunderstorms hold off! ........gone fishing

[skeeter202]

i still say fuel pump , you can replace all three for $100 and if that does not fix it then you are still ahead because sooner or later they will have to be replaced anyway. try running seafoam . i generally put a can between my two tanks every couple months .......

[reelman]

My rig was surging at WOT...dropping back 300-400rpms late 2006... mechanic nailed it right away.. fuel diaphragm leak.. since they are "cheap"... I replaced all of them... happy camper all of 2007.

[utfisherman]

Well, I finally ordered the parts from Boats.net and got 3 pumps, filter, check valve, o-ring, and zip ties shipped for $141. Took about 1 hour to replace. Water tested last week. Less smoke at start up, no sneezing or idle speed decrease when trimmed under, and seems stronger at midrange. I was unable to test full speed, but hopefully the inconsistent top speeds I've experienced will be corrected also. Hopefully this will extend spark plug and O2 sensor lifespans. Glad I waited until the mosquitos quit biting to get rid of the fogger. I'll probably have to stock up on Deep Woods Off before next summer. Thanks for your advice!

[21XDC]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hamfisted &raquo;</TD></TR><TR><TD CLASS="quote">Excessive warts on the powerhead would be another ..... :))

-Mike</TD></TR></TABLE>

LMAO...

[ghind]

A bit late I know...

There are lots of symptoms from blown diaphragms, you may see a fuel slick in the water after the motor has sat for a short while (glassy water). Bad idle, excessive smoke, lost power and blown powerhead.

Not everybody seems to notice there is a problem until the final symptom. Then most people seem to work it out.

This is one of those things that you should just test for yearly.

There are two bolts holding on each fuel pump. If you remote them you can see where the fuel pump gets its pressure pulse from. If it leaks through there, you are leaking raw fuel (no oil) into the crank case. This will dilute your oil mix which is bad.

All you have to do is unboth them, pump the primer bulb and check for leaks, especially leaks that would go into the crank case.

Do not undo the screws that hold the pump together, just remove the bolts from the block. Should test each year at least and as others suggest it is better to replace them proactively.

[utfisherman]

OK, after two outings with the new fuel pumps:
1. Much less smoke upon restart
2. Fuel primer bulb holds it's pressure for over a week vs a few hours
3. Smoother idle
4. More consistent top end speeds

If you are in doubt about weird symptoms, try this fix. You can do it yourself in about an hour for $140 in parts. The mechanic TOTALLY missed this during 2 visits over the last 12 months.